The central 300 pc of our Galaxy is characterized by a strong concentration of warm and dense molecular gas, i.e., the central molecular zone (CMZ; [1]}). Over time, it has become clear that the CMZ contains a number of compact (\(d\!<\!\!10\)  pc) clouds with extraordinary broad-velocity widths (\(\Delta V\!\ge \!50 \)  km s\(^{-1}\) ), which have been named as high-velocity compact clouds (HVCCs; e.g., [2]}, [3]}, [4]}). Some of the HVCCs are considered to have been formed by either multiple supernova explosions in massive stellar clusters ([5]}; [6]}; [7]}) or encounters with massive compact objects ([8]}; [9]}, [10]}, [11]}, [12]}), although most of them do not have any other wavelength counterparts.
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